Not Applicable
Not Applicable
The present invention relates to burnable coils for the control of insects. Insect coils for mosquito and other flying insect control are well known. Conventional coils are typically manufactured by preparing a dough made up of materials that, when dry and ignited, will slowly char, like punk. Conventional coils are treated with an insecticide, repellent, or other insect control active ingredient, most commonly by incorporating the active ingredient in the dough or by surface treating the dough. Coils are formed, usually as a strip of material cut or otherwise formed into a spiral shape, the strip having a substantially uniform cross section from the center of the coil to the outermost end.
D""Orazio, U.S. Pat. No. 4,144,318 is a typical example of such conventional coil technology. D""Orazio describes the formation of a strip of dough throughout which insecticide is uniformly mixed. The strip of dough is subsequently formed into the desired coil shape. Elsner et al., U.S. Pat. No. 5,447,713, describes the formation of a xe2x80x9cboardxe2x80x9d of dough from which coil shapes are punched in much the way that a cookie cutter is used to cut cookies from a rolled-out layer of dough. Elsner et al. also describes surface treatment of either the xe2x80x9cboardxe2x80x9d of dough or of the punched-out coil with a layer of insecticide uniformly and continuously applied with rollers. The disclosures of D""Orazio and Elsner et al. and of all other patents and publications subsequently referred to are incorporated herein by reference.
When the outermost end of a conventional coil is lit, the active ingredient in the as yet unburned portion of coil located immediately beside the burning end is heated and volatilizes. Conventional coils traditionally have been valued in part for their ability to deliver a continuous, linear discharge of volatile ingredient over a considerable length of time, typically three to eight hours or more.
In Kandathil et al., U.S. Pat. No. 5,657,574, however, an insect coil is disclosed wherein the strip of material of which the coil is formed has active ingredient uniformly distributed throughout the material but has a greater cross-sectional area near its outermost end. By this means, the coil is made to deliver active ingredient at a greater rate when it is first lit. This higher, initial dose of active ingredient is intended to quickly establish an effective, insect controlling level of active ingredient in the previously untreated air in the vicinity of the coil. The remainder of the coil shown in Kandathil is of the traditional, generally uniform cross section. Kandathil utilizes the traditional incorporation of active ingredient in the dough from which the coil is formed, causing a continuous release of active ingredient once the coil is lit and a substantially linear release rate after the enlarged initial end has burned.
It is known to provide for doses of perfume delivered to the air for air freshening. Various means for such perfume delivery are known, including, by way of example, by delivering periodic sprays of scent or by continuously moving a web containing separated deposits of volatilizable perfumes over a heater, with each deposit being released only as it approaches the heater. This is done because a human""s ability to perceive scent fatigues if a perfume level is constant, causing a uniform scent level to become progressively less noticeable. In contrast, with periodic scent delivery systems, each new burst of scent is noticed and the effects of olfactory fatigue are lessened.
The insect control active ingredients in an insect coil account for a significant portion of the cost of making the coil. Furthermore, although the active ingredient level dispensed by present day insect coils can easily be both effective and safe to people and animals, in many users"" minds still lower active ingredient levels are appealing, at least if insect control effectiveness is maintained. It can therefore be seen that there is a need for an improved insect coil and method for controlling insects that achieves either (1) insect control at a level comparable to that achievable with conventional coils while, at the same time, requiring only a reduced amount of insect control active ingredient or (2) a higher level of insect control without the need to use an increased amount of insect control active ingredient.
Insect xe2x80x9ccontrolxe2x80x9d is defined to mean killing insects or altering insect behavior. xe2x80x9cInsectxe2x80x9d is defined to include actual insects as well as arachnids and other small animals commonly controlled with insects. Altering insect behavior includes but is not limited to knocking insects down, repelling them, reducing their tendency to bite, altering reproduction or development, and the like. An xe2x80x9cinsect control active ingredientxe2x80x9d is an ingredient that can be volatilized via an insect coil with insect controlling effects. Release of an insect control active ingredient by a burning insect coil shall be deemed xe2x80x9ceffectivexe2x80x9d and in an xe2x80x9ceffective insect controlling amountxe2x80x9d if not less than 50 percent of caged Aedes aegypti mosquitoes are knocked down within 120 minutes upon exposure to the release of the insect control active ingredient in wind-free conditions within a closed, 20 cubic meter chamber. Insects are xe2x80x9cknocked downxe2x80x9d if they are incapacitated and rendered inactive, whether or not actually dead. An insect controlling level of an insect control active ingredient applied to a portion of an insect coil is that amount which causes a release of the insect control active ingredient in effective insect controlling amounts when that portion of the coil is burned.
The invention provides an insect coil having an extended, burnable body. The body may be straight or may be formed into any desired pattern, including but not limited to a spiral, rectangle, or oval. A spiral shape is preferred for its compactness and freedom from sharp turns, which can cause burning anomalies. The body has multiple treated zones each bearing a volatilizable insect control active ingredient in an amount sufficient to achieve insect controlling levels when released and combined with any insect control active ingredient previously released from the insect coil and still present within the area to be protected by the coil. xe2x80x9cMultiplexe2x80x9d is defined to mean at least two. The treated zones are separated from each other by spacing zones that bear a level of insect control active ingredient lesser than that of the treated zones. Consequently, when the insect coil is ignited and the treated zones burn in sequence, the insect coil releases bursts spaced in time of the active ingredient in insect controlling quantities. Preferably, the spacing zones are substantially free of the insect control active ingredient.
In a preferred embodiment, the insect coil of the invention has an ignition end, at which it is to be ignited, and the treated zone closest to the ignition end bears a level of insect control active ingredient greater than that of the remaining treated zones. As a consequence, the first treated zone to burn releases a first amount of the insect control active ingredient larger than amounts released by the subsequent treated zones. The surrounding atmosphere is free of the active ingredient when the first treated zone begins to burn. However, when subsequent treated zones are reached, the surrounding atmosphere may be expected to still contain a residual level of active ingredient from previously burned treated zones. Thus, while a greater initial amount of active ingredient is useful to quickly establish an effective insect controlling amount of active in the air, a lesser amount of active ingredient can be sufficient to merely maintain a pre-established, residual active ingredient concentration at effective levels.
Any insect control active ingredient that can be volatilized via an insect coil with insect controlling effects may be used in the coil of the invention. The art is aware of many such active ingredients. Preferred for reasons of cost and effectiveness are active ingredients selected from the group consisting of pyrethrum, pyrethroids, insect-repelling natural volatile oils, insect growth regulators, and mixtures thereof. The group consisting of pyrethrum, resmethrin, bioallethrin, allethrin, esbiothrin, and mixtures thereof is especially preferred. If desired, selected treated zones of the insect coil of the invention can be treated with an insect control active ingredient different from the insect control active ingredient with which other selected treated zones are treated.
The method of the invention for controlling insects includes the following steps. First, an insect coil is provided having an extended, burnable body. The body has an ignition end and multiple treated zones. Each treated zone bears a volatilizable insect control active ingredient in a quantity that is sufficient to be an effective insect controlling amount of insect control active ingredient when combined with any such active ingredient remaining from a previous release of active ingredient from the insect coil. The treated zones are separated by spacing zones bearing a level of insect control active ingredient lesser than that of the treated zones. The burnable body is placed in the vicinity of insects to be controlled, and the ignition end of the burnable body is ignited. The burnable body is allowed to burn from the ignition end to release bursts spaced in time of the active ingredient in insect controlling quantities. Preferably, the spacing zones are substantially free of the insect control active ingredient. It is even more preferred that the treated zone closest to the ignition end bear a level of insect control active ingredient greater than that of the remaining treated zones.